Getting Error: 'Indexing knn vector fields is rejected as circuit breaker triggered. Check _opendistro/_knn/stats for detailed state'

Im not sure why this error is coming, but when I created 2nd KNN index, and try to index first document, I encounter this error, and I check the ‘_opendistro/_knn/stats’ and I found some stats as following:

"graph_memory_usage_percentage": 98.00549,
"graph_query_requests": 6866,
"graph_memory_usage": 3763893,

And my memory utilisation is 96% and my first KNN index’s total size is 100GB, does it related to it.

I don’t how in which direction I think, can someone help me to find out and resolve the issue?